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Mauer, 29, soon will enter the third year of an eight-year, $184 million deal that pays him $23 million annually.

In 147 games this past season, Mauer hit .319 with 10 homers, 85 RBIs and an AL-best .416 on-base percentage. He set a new career high for games played after battling injuries in recent seasons and being limited to just 82 games in 2011.

The Red Sox already have added backup catcher David Ross in free agency this offseason, and they also have catchers Jarrod Saltalamacchia and Ryan Lavarnway on their roster. After shedding the mega-contracts of first baseman Adrian Gonzalez, left fielder Carl Crawford and righthander Josh Beckett last August, Boston has some payroll flexibility.